The invention relates to novel polyalkylpiperidine derivatives exhibiting an OH group on the hindered nitrogen atom of the piperidine ring and a diversity of substituents on the 4-position of the ring.
Various N-hydroxy derivatives of hindered amines are known. For example, a substantial number of such derivatives are generically disclosed in U.S. Pat. No. 4,590,231. The substituents on the 4-position include ether, ester, amino, dioxaspiro, diaza-dione, urea and triazine substituents, among others. These derivatives are identified as stabilizers in polyolefin compositions. Mono- and di-piperidinyl ester derivatives are likewise disclosed in Japanese 54-69162 for use in stabilizing urethane polymers. Other N-hydroxy derivatives are disclosed in Chemical Abstracts 74, 64180u (1971); J. Poly. Sci., Polymer Chem. Ed. 22, 227-81 (1984); Polym. Sci. Technol. 26, 35-47 (1984); and Zh. Org. Khim. 6, 2365-9 (1970); as well as in U.S. Pat. No. 3,936,456, U.S. Pat. No. 4,404,302 and U.S. Pat. No. 4,472,547.
Accordingly, it is the object of the instant invention to identify a series of new N-hydroxy hindered amines having a broad range of stabilization performance characteristics.
These derivatives thus correspond to the formula ##STR1## wherein R is hydrogen or methyl;
m is 1-4;
when m is 1, R.sub.1 is ##STR2## where x is 0 or 1 and R.sub.4 independently are C.sub.1 -C.sub.8 alkyl, or ##STR3## with y is 2-4;
when m is 2, R.sub.1 is ##STR4## wherein D.sub.1 and D.sub.2 are independently C.sub.1 -C.sub.8 alkyl, C.sub.6 -C.sub.10 aryl, C.sub.7 -C.sub.12 aralkyl or 3,5-di-t.butyl-4-hydroxybenzyl and D.sub.2 is also hydrogen, D.sub.3 is C.sub.1 -C.sub.18 alkyl or C.sub.2 -C.sub.18 alkenyl, and D.sub.4 is C.sub.5 -C.sub.12 cycloalkylene;
when m is 3, R.sub.1 is a trivalent acyl radical of an aliphatic, unsaturated aliphatic, cycloaliphatic or aromatic tricarboxylic acid;
when m is 4, R.sub.1 is a tetravalent acyl radical of a saturated or unsaturated aliphatic or aromatic tetracarboxylic acid;
The the formula, representative alkyl groups include methyl, ethyl, n-propyl, n-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-undecyl and n-dodecyl; aryl includes phenyl and naphthyl; aralkyl includes benzyl, alpha-methylbenzyl and phenethyl; and alkenyl includes 1-propenyl, allyl, methallyl, 2-butenyl, 2-hexenyl and 2-octenyl. R.sub.1 as a trivalent acyl radical is, for example, an acyl radical of benzene-1,2,4-tricarboxylic acid. R.sub.1 as a tetravalent acyl radical is, for example, an acyl radical of 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-but-2-enetetracarboxylic acid and 1,2,3,5- and 1,2,4,5-pentanetetracarboxylic acid. In the R.sub.1 members when m is 2, malonates are preferred where D.sub.1 is lower alkyl and D.sub.2 is hydrogen or lower alkyl.
The hydroxylamine derivatives of this invention are generally prepared by oxidizing the corresponding N-H hindered amine with an appropriate peroxy compound such as hydrogen peroxide or tert-butyl hydroperoxide in the presence of molybdenum oxide or a metal carbonyl or metal oxide catalyst followed by reduction of the oxyl intermediate formed thereby to the desired N-hydroxy derivative, preferably by catalytic hydrogenation. Molybdenum (VI) is noted to increase the efficiency of the oxidation step. The reaction is preferably conducted in hydrocarbon solvents such as toluene. The starting materials needed to prepare the derivatives of this invention are items of commerce or can be prepared by known methods.
The derivatives are particularly effective in stabilizing organic materials primarily against the degradative effects of actinic stimuli. Such organic materials include polyolefins, vinyl chloride polymers, elastomers, polyesters and polyurethanes. They are particularly applicable for the stabilization of ambient cured and acid catalyzed thermoset coatings or enamels wherein they improve the durability and weatherability of the ambient cured systems and wherein they do not inhibit or interfere with cure in acid catalyzed systems in view of their reduced basicity.
The following examples illustrate the embodiments of this invention.